Mosquito-transmitted diseases are a major cause of suffering and death in the tropical world. Malaria alone, kills one to two million people every year. The urgency for developing new control strategies is underscored by the development of resistance by parasites to previously effective drugs, by the resistance of mosquitoes to a variety of insecticides, and by the lack of an effective vaccine. Inhibition of the parasite's life cycle in the mosquito is a strategy that requires more attention. This proposal focuses on the gut of the human malaria vector, Anopheles gambiae. The gut is the first site of interaction between Plasmodium and the mosquito. Ingestion of blood by the adult mosquito triggers the secretion of a peritrophic matrix (PM), which is a thick extra-cellular sheath that completely surrounds the blood meal and any ingested parasites. The PM poses a partial barrier for malaria parasite invasion. Modifications of the PM may lead to a more complete barrier to infection. To devise such strategies will require a thorough molecular characterization of the PM, and a more complete understanding of its structure and function. The major objectives of this proposal are to isolate and characterize genes encoding PM proteins, to investigate how PM proteins interact for the assembly of the PM, and to probe into the physiological role of the PM. Specifically, PM genes will be cloned by screening expression libraries with anti-PM antibodies or based on amino acid sequence of fractionated PM proteins. Interaction between PM proteins will be measured in vivo using the yeast two-hybrid system or in vitro using affinity blotting techniques. Antibodies to recombinant PM proteins will be used to determine if PM proteins are stored in secretion vesicles. The thickness and porosity of the PM will be experimentally altered to measure the effects on digestion and on the ability of parasites to traverse the PM. Genetic transformation of Ae. aegypti is already possible and transformation of An. gambiae is likely to become available in the near future. The characterization of PM protein genes and an understanding of their function may lead to novel strategies for malaria control.